1. Field of the Invention
The present invention relates to a piezo-electric speaker using a piezo-electric member.
2. Description of Background Art
In a conventional piezo-electric speaker, a piezo-electric vibration plate having the piezo-electric member is directly secured to a case and the sound is propagated to the ambient air by the acoustic vibration caused by the piezo-electric vibration plate. In this case, the case is formed by a no-resonant rigid body.
However, in the conventional piezo-electric speaker the size of the piezo-electric vibration plate is limited since it is difficult to make a piezo-electric member of a large area due to the difficulty of assuring the strength of a thin piezo-electric porcelain used for the piezo-electric member. Accordingly, it is difficult to generate the sound of low frequency range at a predetermined volume without using the acoustic vibration of a large area. Although the sound of high frequency range could be generated if the piezo-electric member having a large area would be formed with increasing its thickness, it is also difficult to generate the sound of high frequency range since the high frequency response is detracted due to the increased thickness of the piezo-electric member.